The economy of California – poised to create a market for legal marijuana – could see its economy boosted by as much as $5bn, according to a new study.

The report by the University of California Agricultural Issues Centre, says that the legalisation of the drug will provide the state a further reason for tourists – or at least some tourists – to visit.

Yet it also warns that around 30 per cent of people who use cannabis may remain in the illegal market, in order to avoid the financial impact of regulations that require marijuana to be tested, tracked and taxed at 15 per cent of its retail value.